1. Field of the Invention
The present invention pertains to binoculars in which at least one of the two optical systems is moved horizontally in directions perpendicular to the optical axes to perform pupil distance adjustment.
2. Description of the Prior Art
Conventionally, a method of performing dioptric adjustment by moving an eyepiece lens has offered the simplest construction and has been the mainstream approach. The mechanism is such that an one eyepiece lens system and the main body of the binoculars are connected via a screw mechanism, wherein when the eyepiece lens and the eyepiece lens holder that integrally holds said eyepiece lens are turned, the eyepiece lens system moves along the optical axis relative to the object optical system and dioptric adjustment is carried out. However, because the operating member to perform dioptric adjustment is located near the eyepiece lens, there is a possibility that it may be moved by mistake while using the binoculars, which creates an inconvenience.
With this as a backdrop, an object lens dioptric adjustment mechanism has been proposed in which dioptric adjustment is performed using the object lens. For example, Japanese Published Utility Model Application SHO 57-22163 discloses a construction in which two rods are linked to the two object lenses such that when the rods are moved together along the optical axes, both object lenses move and focus adjustment is performed, and when one pre-specified rod is moved, only one object lens moves and dioptric adjustment is carried out.
In the conventional binoculars described above, a rotational pupil distance adjustment mechanism is employed in which the distance between the right and left optical systems (hereinafter termed the pupil distance') is adjusted by rotating the optical systems around one or two shafts. In contrast, particularly with binoculars made compact and thin, those using a horizontal pupil distance adjustment mechanism are known in which one of the two optical systems is horizontally moved in directions perpendicular to the optical axes. Dioptric adjustment in binoculars using this horizontal pupil distance adjustment mechanism is also performed using the eyepiece lens.
In doing so, where the optical system comprises round lenses, the eyepiece lens and its holder may be rotated to perform dioptric adjustment. However, where the lenses are made non-round by cutting off the top and bottom ends in order to make the binoculars thinner, it is difficult to rotate the optical system, and therefore a dioptric adjustment mechanism must be used in which the eyepiece lens is horizontally moved by externally rotating a dial, etc.
Consequently, binoculars having a horizontal pupil distance adjustment mechanism cannot help but become complex in their construction. In addition, because dioptric adjustment in binoculars having the horizontal pupil distance adjustment mechanism is performed by moving the eyepiece lens, as described above, the operating member to perform dioptric adjustment is located near the eyepiece lens, and as a result it may be moved by mistake while using the binoculars.
It would thus be preferable for dioptric adjustment to be performed using the object lens. However, the conventional object lens dioptric adjustment mechanism is based on binoculars using the single-shaft or double-shaft rotational pupil distance adjustment mechanism and does not accommodate binoculars using the horizontal pupil distance adjustment mechanism. In addition, since the main purpose of binoculars using the horizontal pupil distance adjustment mechanism is compactness, unless the operating members for focus adjustment and dioptric adjustment are located at appropriate positions easy to access, operational errors might result.